1. Field of the Invention
This invention relates to the flame treating of a material web.
2. Description of the Prior Art
The flame treating of a material web to facilitate adherence of another substance to the web is well known.
Wise, U.S. Pat. No. 3,870,461 discloses an apparatus and method for flame treating in which gas is mixed with sufficient air prior to ignition to insure complete combustion and an intense and lean flame with no flame wrap around or unignited gas imbedded in the web material.
Wise U.S. Pat. No. 3,390,465 discloses heat treating of a moving web having a surface coating dried thereon and using an abundance of air to wipe off volatile by-products.
U.S. Pat. No. 3,640,788 discloses a method of flame treatment utilizing a stiff flame fed by a combustible mixture of gas and air at a ratio to obtain substantially complete combustion of the mixture at the flame tip.
A problem experienced with many of the prior art devices has been thermal bow along the length of the burner. Such bow results in uneven flame positioning across the web and thus, uneven flame treatment of the web.
One approach, such as disclosed in U.S. Pat. No. 3,411,717 is the use of water tubes running adjacent and parallel to the length of burner to produce a more equal temperature along the length of the burner thereby minimizing the bow.
The burner disclosed herein is designed to minimize the thermal bow along the length of the burner. The tube within a tube construction of the burner in the present invention provides longitudinal rigidity to the burner. Further, a heat sink chamber is formed within the burner holding the fuel mixture flowing from the outlets of the inner tube and allowing heat transfer from the portion of the outer tube adjacent the chamber into the mixture reducing the temperature of the outer tube while minimizing the temperature differences of portions of the outer tube.
Many of the prior art devices provide for continuously feeding a material web at relatively high speed to and past a burner which directs a flame fed by a combustible mixture of gas and air. A major disadvantage of many of the prior art devices is that the burner often produces a flame of uneven intensity, resulting in the flame contacting only a portion of the web and unevenly treating the web. One approach, such as disclosed in U.S. Pat. No. 3,334,820 is the use of gas burners with selective flame distribution so as to obtain fairly uniform heat conditions along the length of the material web. The burner disclosed herein is designed to produce a lean flame of relatively high velocity thereby treating all the facing web surface minimizing the uneven treatment of the web.
Another problem of many of the prior art devices is that the material web is traveling at so substantial a velocity relative to the flame velocity to result in the web pulling the flame downstream as the web travels along its path and as a result of the flame dwelling on the web, the web material may become brittle. The present invention seeks to minimize the damage of flame/web dwell by moving the web past the flame at a web velocity equal to or greater than a minimum high velocity of the gas/air mixture.